This shared instrumentation grant proposal is for the purchase of a dedicated small-animal PET scanner. The NIH-funded research projects that require this system are aimed primarily at developing new molecular imaging agents and validating existing radiotracers for the investigation of fundamental biological processes and the assessment of the impact of therapeutic interventions. The system will be located in the Center for Small Animal Imaging (CSAI) alongside systems representing the major in vivo imaging modalities (ultrasound, bioluminescence/fluorescence, SPECT, MRI and MRS). The CSAI functions as a Core Facility for the university and operates as part of the Vanderbilt University Institute of Imaging Science. The PET system will be supported by an experienced group of imaging scientists and a highly qualified support staff. It also will be a key resource for predoctoral and postdoctoral trainees supported by our institutional training grants in cancer imaging as well as our other trainees in imaging science.